This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The perinatal environment influences development of the respiratory control system in mammals and birds. We have been studying a model of developmental plasticity in which rats or quail are exposed to normobaric hyperoxia (60% oxygen) during development. These animals exhibit attenuated ventilatory responses to acute hypoxia as adults owing to abnormal development of the carotid body, but the cellular and molecular mechanisms by which hyperoxia alters carotid body development are only beginning to be revealed. Preliminary studies suggest that hyperoxia may impair carotid body development by changing the expression of neurotrophic factors or their receptors and/or by influencing genes that regulate the cell cycle. The proposed experiments address these hypotheses in rats, mice and quail, thereby providing valuable new insights into the role of the environment in the normal and pathological development of the respiratory control system. Abnormal development of the respiratory control system is implicated in many clinical disorders, so it is critical to understand how environmental conditions in early life influence protective ventilatory reflexes. Furthermore, this project enables undergraduate students to participate directly in biomedical research and fosters collaborations with regional scientists using similar or complementary research approaches.